Keith Edmunds wrote:
> We're seeing some odd sizes reported for incremental backups. A 'status
> jobs' shows, firstly, for a full backup:
>
> 338 Full 19,796,396 2.916 T OK 06-Apr-09 04:07 Client1
>
> That looks right: nearly 20 million files and nearly 3Tb.
>
> Now an incremental:
>
> 340 Incr 1,085 1.313 T OK 07-Apr-09 13:10 Client1
>
> Just over a thousand files (believable) but 1.3Tb of data (not
> believable). That would suggest an average file size of over a gigabyte
> whereas the full back suggests an average file size of around 150K, which
> is much more believable.
I think you are making a problematic assumption here - namely that the
the files backed up in the incremental represent a representative sample
of the files overall. In reality, by nature the files in an incremental
backup are very different from the files in a full backup. For instance,
you will almost never see the (relatively small) files in /usr/bin
backed up in an incremental. On the other hand, maybe one of the 1085
files in the incremental is a 1 TB database that is accessed daily? Or
some other large file that is in regular use.
The only way to find out whether or not this is legitimate is to
actually query bacula for the list of files in the job.
> Quite apart from anything else, it's unlikely that 1.3Tb would even fit on an
> AIT5 tape.
>
I don't see a problem here. As long as the data very is compressible, it
could fit quite comfortably. It actually supports my suspicion that it
may be a single large database file; database files can often be
compressed to as little as a few percent of their original size, because
they are often sparse files.
--
Kevin Keane
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